Art of separating patent leather surfaces



June 12, 1934. s. J. COUGHLIN ART OF SEPARATING PATENT LEATHER SURFACES Fi'led Nov. 22. 1932 Patented June 12, 1934 UNETED STATES ART OF SEPARATING PATENT LEATHER SURFACES Stuart J. Coughlin, Georgetown, Mass., assignor to United Shoe Machinery Corporation, Paterson, N. J a corporation of New Jersey Application November 22, 1932, Serial No. 643,943

9 Claims.

This invention pertains to methods of and ap paratuses for separating stuck-together patent leather surfaces. It is to be understood, however, that the invention and various important characteristics and features thereof may have other applications and uses.

In the manufacture of patent leather, also called japanned and enameledleather, the tanned skin is usually given a body coating comprising one or more coats of dressing, known as daub coats, and after these first coats have dried a socalled flow coat is applied, the latter being followed by a finish coat of varnish-like character. The coated leather is then baked in an oven at a temperature of about 160 F. for fourteen hours more or less. After being subjected to treatment by ultra-violet radiation from either the natural or an artificial source for the desired length of time, the coated surface of the finished leather is apparently dry and substantially free from tackiness. However, it is easily marred if rubbed or scratched, and when subjected to pressure, particularly if warm, this finished surface tends to adhere to objects with which it contacts. To avoid injury to this highly finished surface during storage or transportation, it is customary to place a pair of skins with their smooth surfaces in contact and in this paired relation to pack them for shipment or storage. If, when so paired, the skins are piled in such manner that the lower ones are subjected to considerable pressure, the latter are apt to stick or adhere to each other, particularly if the room in which they are stored be warm. Although many expedients have been tried for preventing this action, as for example by oiling the skins, none of these prior attempts has proven satisfactory, and the only known way to avoid loss has been to separate the skins at frequent intervals. However, this is not always possible, since the skins are often shipped long distances, and if the separation be delayed too long the skins adhere so firmly that they can not be separated satisfactorily by any method heretofore known. All attempts to strip such firmly stuck-together skins from each other have resulted either in pulling off part of the coating from one or the other skin, which ruins the skin for its intended use, or in damage to the body of the leather, such as greatly to reduce its value. The futility of attempting to separate such stuck-together skins is so well recognized that heretofore it has been common to sell such skins for their value as fertilizer material, which ordinarily is but an insignificant fraction of their original value as leather.

After much experiment I have devised a meth- 0d, and an apparatus useful in practising the method, whereby finished patent leather skins that have been stuck together, even for periods of several years, may be separated without damage either to the surface finish or to the body of i I the leather, leaving the surface with as high, if not an even higher, luster than that which was originally given to it by the finisher. By finished patent leather is meant leather having varnished surfaces which have undergone baking in ovens and solarizing, the latter covering treatment by ultraviolet radiation from the sun or from an artificial source. The method is also of great value and importance in the separation of skins at temperatures below that best suited for handling patent leather and where the paired skins, although not stuck to such a degree as actually to prevent separation, develop incipient cracks when peeled apart at the low. temperature prevailing. evident during the separation of the skins, they become evident in subsequent operations, for example in lasting, where the leatheris subjected to very considerable tension. By the use of the present apparatus the skins may be raised to the proper working temperature and may be separated without danger of developing such incipient cracks, and thereafter, when employed in making shoes, the skins are capable of withstand- While such cracks are not necessarily ing much harsher treatment without developing cracks, blisters or other defects in the finish than leather which is handled too cold in the preliminary processes. a

The improved method comprises the step of subjecting both skins simultaneously to heat applied to the flesh or outer surfaces of the skins at a substantially'uniform temperature of the desired degree for a predetermined length of time. The result is to soften both finish coats to substantially the same degree at the same instant.

Promptly while the skins still retain the absorbed heat they are stripped apart by a direct pull, conveniently exerted upon one skin while holding the other stationary. Preferably the stripping operation is so conducted as to peel one skin from the other in such a manner that the line of separation is always substantially straight across the entire width of the skin. In the prac tice of the method, the skins are subjected to a relatively gentle heat, within a definite narrow range of temperatures, for a definite period of time, and I apprehend that the results attained are to some extent at least dependent upon the relatively slow application of moderate heat,

about 185 F., over the whole exposed surfaces of heated rolls. By the latter method it would be dimcult if not impossible to obtain the desired uniformly softened condition of the finish coats as a preliminary to the operation of stripping the skins apart. I also believe from the results of my experiments that the application of heat to opposite sides of the pair of skins simultaneously is an important factor in the results attained for the reason that in this way the heat reaches the finish coats of varnish through both skins at substantially the same time without necessitating excessive heating of the daub coat of one skin as might be the case if the heat were applied to one side only. Undue softening of the daub coat of one skin might quite readily result in the removal of the whole daub and finish coats from that skin during the stripping operation. When properly performed this process produces a perfect separation of the skins without injury to the finish coat or surface or any damage whatever to the skin itself.

For practising the method there is provided, in the illustrated construction, an oven arranged to be heated very uniformly to a definite tempera-- ture, conveniently by electrical heating units.

. For introducing the skins into the oven there is provided a horizontally movable carriage having a perforated or foraminous work-supporting surface upon which the stuck-together skins are laid. Preferably and as shown, means are provided for attaching the lower skin to the carriage to facilitate subsequent separation of the skins from each other. The skins are introduced into the oven on the carriage and supported thereby while undergoing the heat treatment, the foraminous work supporting surface permitting access of heat to the lower surface of the work. After a proper period of treatment the carriage is withdrawn and one edge of the upper skin is seized, preferably by operators stationed at opposite sides of the carriage (or alternatively by suitable mechanical means), and the upper skin is then rapidly peeled off from the lower one, the finish. or varnish coating becoming glossy and hard almost instantaneously as it is exposed to the air. In this way and by apparatus of this or equivalent character it is possible to separate and reclaim skins which have been apparently hopelessly stuck, thus converting material usually considered worthless into a valuable product. In fact, after this treatment, the skins show less tendency to stick than before so that I contemplate the advantageous employment of the apparatus and of the described method of applying heat in the treatment of patent leather before the surfaces have become stuck together in order to prevent such sticking.

These and other important characteristics and features of the invention, together with novel combinations of parts, will now be described in detail in the specification and then pointed out more particularly in the appended claims.

In the drawing,

Fig. 1 is a side view partly in section of an apparatus illustrating diagrammatically one embodiment of the invention;

Fig. 2 is a vertical section substantially on the line 2-2 of Fig. 1; and

Fig. 3 is a fragmentary view of the supporting carriage illustrating a means for securing the end of one skin while the other is peeled off.

In the illustrated construction designed for use particularly in the treatment of patent leather, the numeral 1 designates an oven made of sheet metal, although any other suitable material may be used. Preferably and as shown, the outside walls of the oven are covered with heat insulating material 2a. As illustrated, this oven is furnished at both ends with normally closed doors 2 and 3, respectively, which may be raised to admit the skins to be treated.

At opposite sides of the oven, and preferably somewhat nearer the top than the bottom, I provide spaced parallel horizontal guide rails 4 and 5. These rails form supporting and guiding means for a carriage 6 which may be introduced into the oven through either one or the other of the doors 2 or 3 and which is preferably provided with rollers or wheels which rest upon the rails 4 and 5. Conveniently a table or work support indicated at T is provided outside of the oven for supporting the carriage 6 when the latter is withdrawn from the oven, it being obvious that suitably supported guide rails similar to rails 4 and 5 may be substituted for the table T.

While the carriage 6 may be of any convenient construction, it is shown as comprising a substantially horizontal foraminous supporting member 7 upon which the skins to be separated may be placed. Conveniently this member '7 consists of a piece of wire screen stretched smoothly between suitable members of the carriage frame, although I contemplate that substantially the same results may be secured by the use of supporting means of different character, provided that such supporting means freely exposes the under surface of the skin resting thereon. Preferably and as shown, one end member of the carriage frame is provided with retaining means comprising downwardly projecting prongs 8 adapted to engage and hold one end of the lowermost of the pair of skins resting upon the support 7.

Beneath the horizontal plane defined by the rails 4 and 5, there is provided one or more bailie plates 9 suitably supported in any desired manner and beneath which I place heating elements as indicated at l0, l1 and 12. Conveniently these heating elements are of electrical type consisting of ribbons of resistant material adapted to become hot when an electrical current passes through them. The elements 10 are the main heating elements, while the elements 11 and 12, disposed nearer to the doors, are intended primarily to compensate for any air leakage around the doors.

While I prefer to employ electrical heating means I contemplate that other equivalent means may be employed if desired, for example steam coils, gas flames, or the like. However, as it is very important that the temperature within the housing or oven be kept substantially uniform and within a very definite temperature range, the heating means of whatever nature provided is placed under the control of automatic thermostatic elements 13 arranged within the oven. I find through experiment that a temperature of 185 F. is apparently best suited for the satisfactory performance of this process and while I contemplate that a variation of a few degrees upon either side of this preferred temperature may be permissible, I find that any substantial departure from this temperature results in failure, since a lower temperature fails to soften the varnish coat sufficiently within a reasonable period of time, while a higher temperature causes the body or daub coat to soften to such an extent that it is apt to pull oif and thus ruin the skin.

In the operation of this device, I first bring the temperature within the oven tothe desired point and then, with the carriage resting upon the support T, I lay a pair of stuck-together skins upon the supporting member 7 of the carriage and cause the retaining elements 8 to penetrate or otherwise grip an edge portion of the lower of the pair of skins. The door 2 of the oven is then opened and the carriage is pushed into the enclosure, moving along upon the rails 4 and 5. When the carriage is wholly within the oven the door 2 is closed and as the opening of the door permits the temperature within to drop slightly I permit the carriage to remain within the oven until the temperature has been restored to the desired degree and then for a predetermined further period, of the order of one minute or thereabouts, which I find is suflicient for the purpose. During this time the outer or flesh surfaces of both skins are subjected to a substantially uniform temperature throughout their entire areas, the warmth penetrating inwardly from these flesh surfaces toward the finish varnish coats so that by the time the latter are properly softened the skins are warmed thoroughly throughout. The carriage is now withdrawn quickly from the oven and an operator stationed at each side of the carriage seizes that corner of the upper skin S (Fig. 3) which is nearest to him and which is above the end of the lower skin S that is secured to the retainers 8. The operators then exert a pull in the direction of the arrow A indicated in Fig. 3 so as to peel the upper skin backwardly and strip it from the lower skin.

In performing this operation the operators at opposite sides should exert a substantially equal pull so that the line of separation of the two skins will always be substantially straight across the entire width of the skin. While thus convenient- 1y performed manually, I contemplate the use of mechanically operated stripping meansas with in the scope of the invention. This stripping operation should be performed very rapidly and While the heat is still retained in the skins. When the skins are so stripped I find that the surface coatings are uninjured and in fact apparently in better condition than the finish originally imparted to the skins. Moreover, I find that skins allowed to become cool after being separated in the manner described, do not show as great a tendency to stick again when placed in pairs as do skins which have just been finished. For this reason I contemplate using the described method of heat treatment in heat treating patent leather shortly after its manufacture, that is, after it has been baked and solarized, as a preventative of sticking as well as in separating skins which have become stuck together.

While I have disclosed certain apparatus as desirable for carrying out my process I contemplate that apparatus of other and equivalent character may be employed and that the stuck-together skins may be raised to the desired temperature by other specific means than that here disclosed and that all such equivalent apparatus and means fall within the scope of my invention.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. That improvement in methods of separating a pair of stuck-together patent leather skins which comprises subjecting the entire exposed surfaces of the leather to a temperature of approximately 185 F. until the finish coats or surfaces are softened to the desired degree, and then peeling one skin from the other.

2. That improvement in methods of separating a pair of stuck-together patent leather skins which comprises warming the skins to a substantially uniform temperature such that the finish coats of both skins are softened but without substantially softening the body or daub coating of the skins, and then peeling one skin from the other while the finish coats are soft.

3. That improvement in methods of separating a pair of stuck-together patent leather skins which comprises subjecting the entire outer surfaces of both skins simultaneously to a substantially uniform heat within definite limits of temperature range for a predetermined time such as to soften the finish coats of varnish but without substantially softening the body or daub coats, and stripping the skins apart while the finish coats are still soft by a pull exerted in such a way that the line of separation is always substantially straight across the entire width of the skin.

4. That improvement in methods of separating a pair of patent leather skins which comprises simultaneously warming the entire flesh surfaces of both skins to a substantially uniform temperature such that the finish coats of both skins are softened, and peeling one skin from the other while the finish coats are soft.

5. That improvement in methods of treating finished patent leather surfaces to prevent sticking which comprises heating the previously baked and solarized patent leather uniformly to a degree of temperature such as to soften the finish coat without softening the body or daub coat, and permitting the skin and particularly the finish coat thereof to cool rapidly by exposure to the air.

6. An apparatus for use in separating a pair of stuck-together patent leather skins which comprises means for subjecting the entire exposed surfaces of the skins to a temperature of approximately 185 F., and means for retaining one skin stationary while peeling the other from it.

7. An apparatus for use in separating a pair of stuck-together patent leather skins which comprises an oven having electrical heating units therein arranged to maintain a substantially uniform temperature in the oven, and a carriage movable into and out of the oven, said carriage having a foraminous support for the skins and also gripping means for engagement with an edge portion of one skin.

8. An apparatus for use in separating a pair of stuck-together patent leather skins which comprises an oven having electrical heating units therein arranged to maintain a substantially uniform temperature in the oven, a carriage movable into and out of the oven, and guide means within the oven for the carriage, said carriage having a foraminous support for the skins and also gripping means for engagement with an edge portion of one skin.

9. An apparatus for use in separating stucktogether patent leather skins which comprises a frame provided with a foraminous support upon which the skins may rest, retaining elements carried by the frame and adapted for holding engagement with one edge of that skin which contacts with the support, and means arranged to provide a uniformly warm atmosphere of substantially 185 F. surrounding the frame with the skins thereon.

STUART J. COUGI-ILIN. 

